/*
x86 function call convention, 64-bit:
-------------------------------------
arguments | callee-saved | extra caller-saved | return
[callee-clobbered] | | [callee-clobbered] |
---------------------------------------------------------------------------
rdi rsi rdx rcx r8-9 | rbx rbp [*] r12-15 | r10-11 | rax, rdx [**]
( rsp is obviously invariant across normal function calls. (gcc can 'merge'
functions when it sees tail-call optimization possibilities) rflags is
clobbered. Leftover arguments are passed over the stack frame.)
[*] In the frame-pointers case rbp is fixed to the stack frame.
[**] for struct return values wider than 64 bits the return convention is a
bit more complex: up to 128 bits width we return small structures
straight in rax, rdx. For structures larger than that (3 words or
larger) the caller puts a pointer to an on-stack return struct
[allocated in the caller's stack frame] into the first argument - i.e.
into rdi. All other arguments shift up by one in this case.
Fortunately this case is rare in the kernel.
For 32-bit we have the following conventions - kernel is built with
-mregparm=3 and -freg-struct-return:
x86 function calling convention, 32-bit:
----------------------------------------
arguments | callee-saved | extra caller-saved | return
[callee-clobbered] | | [callee-clobbered] |
-------------------------------------------------------------------------
eax edx ecx | ebx edi esi ebp [*] | <none> | eax, edx [**]
( here too esp is obviously invariant across normal function calls. eflags
is clobbered. Leftover arguments are passed over the stack frame. )
[*] In the frame-pointers case ebp is fixed to the stack frame.
[**] We build with -freg-struct-return, which on 32-bit means similar
semantics as on 64-bit: edx can be used for a second return value
(i.e. covering integer and structure sizes up to 64 bits) - after that
it gets more complex and more expensive: 3-word or larger struct returns
get done in the caller's frame and the pointer to the return struct goes
into regparm0, i.e. eax - the other arguments shift up and the
function's register parameters degenerate to regparm=2 in essence.
*/
/*
* 64-bit system call stack frame layout defines and helpers, for
* assembly code (note that the seemingly unnecessary parentheses
* are to prevent cpp from inserting spaces in expressions that get
* passed to macros):
*/
#define R15 (0)
#define R14 (8)
#define R13 (16)
#define R12 (24)
#define RBP (32)
#define RBX (40)
/* arguments: interrupts/non tracing syscalls only save up to here: */
#define R11 (48)
#define R10 (56)
#define R9 (64)
#define R8 (72)
#define RAX (80)
#define RCX (88)
#define RDX (96)
#define RSI (104)
#define RDI (112)
#define ORIG_RAX (120) /* + error_code */
/* end of arguments */
/* cpu exception frame or undefined in case of fast syscall: */
#define RIP (128)
#define CS (136)
#define EFLAGS (144)
#define RSP (152)
#define SS (160)
#define ARGOFFSET R11
#define SWFRAME ORIG_RAX
.macro SAVE_ARGS addskip=0, norcx=0, nor891011=0
subq $9*8+\addskip, %rsp
CFI_ADJUST_CFA_OFFSET 9*8+\addskip
movq %rdi, 8*8(%rsp)
CFI_REL_OFFSET rdi, 8*8
movq %rsi, 7*8(%rsp)
CFI_REL_OFFSET rsi, 7*8
movq %rdx, 6*8(%rsp)
CFI_REL_OFFSET rdx, 6*8
.if \norcx
.else
movq %rcx, 5*8(%rsp)
CFI_REL_OFFSET rcx, 5*8
.endif
movq %rax, 4*8(%rsp)
CFI_REL_OFFSET rax, 4*8
.if \nor891011
.else
movq %r8, 3*8(%rsp)
CFI_REL_OFFSET r8, 3*8
movq %r9, 2*8(%rsp)
CFI_REL_OFFSET r9, 2*8
movq %r10, 1*8(%rsp)
CFI_REL_OFFSET r10, 1*8
movq %r11, (%rsp)
CFI_REL_OFFSET r11, 0*8
.endif
.endm
#define ARG_SKIP (9*8)
.macro RESTORE_ARGS skiprax=0, addskip=0, skiprcx=0, skipr11=0, \
skipr8910=0, skiprdx=0
.if \skipr11
.else
movq (%rsp), %r11
CFI_RESTORE r11
.endif
.if \skipr8910
.else
movq 1*8(%rsp), %r10
CFI_RESTORE r10
movq 2*8(%rsp), %r9
CFI_RESTORE r9
movq 3*8(%rsp), %r8
CFI_RESTORE r8
.endif
.if \skiprax
.else
movq 4*8(%rsp), %rax
CFI_RESTORE rax
.endif
.if \skiprcx
.else
movq 5*8(%rsp), %rcx
CFI_RESTORE rcx
.endif
.if \skiprdx
.else
movq 6*8(%rsp), %rdx
CFI_RESTORE rdx
.endif
movq 7*8(%rsp), %rsi
CFI_RESTORE rsi
movq 8*8(%rsp), %rdi
CFI_RESTORE rdi
.if ARG_SKIP+\addskip > 0
addq $ARG_SKIP+\addskip, %rsp
CFI_ADJUST_CFA_OFFSET -(ARG_SKIP+\addskip)
.endif
.endm
.macro LOAD_ARGS offset, skiprax=0
movq \offset(%rsp), %r11
movq \offset+8(%rsp), %r10
movq \offset+16(%rsp), %r9
movq \offset+24(%rsp), %r8
movq \offset+40(%rsp), %rcx
movq \offset+48(%rsp), %rdx
movq \offset+56(%rsp), %rsi
movq \offset+64(%rsp), %rdi
.if \skiprax
.else
movq \offset+72(%rsp), %rax
.endif
.endm
#define REST_SKIP (6*8)
.macro SAVE_REST
subq $REST_SKIP, %rsp
CFI_ADJUST_CFA_OFFSET REST_SKIP
movq %rbx, 5*8(%rsp)
CFI_REL_OFFSET rbx, 5*8
movq %rbp, 4*8(%rsp)
CFI_REL_OFFSET rbp, 4*8
movq %r12, 3*8(%rsp)
CFI_REL_OFFSET r12, 3*8
movq %r13, 2*8(%rsp)
CFI_REL_OFFSET r13, 2*8
movq %r14, 1*8(%rsp)
CFI_REL_OFFSET r14, 1*8
movq %r15, (%rsp)
CFI_REL_OFFSET r15, 0*8
.endm
.macro RESTORE_REST
movq (%rsp), %r15
CFI_RESTORE r15
movq 1*8(%rsp), %r14
CFI_RESTORE r14
movq 2*8(%rsp), %r13
CFI_RESTORE r13
movq 3*8(%rsp), %r12
CFI_RESTORE r12
movq 4*8(%rsp), %rbp
CFI_RESTORE rbp
movq 5*8(%rsp), %rbx
CFI_RESTORE rbx
addq $REST_SKIP, %rsp
CFI_ADJUST_CFA_OFFSET -(REST_SKIP)
.endm
.macro SAVE_ALL
SAVE_ARGS
SAVE_REST
.endm
.macro RESTORE_ALL addskip=0
RESTORE_REST
RESTORE_ARGS 0, \addskip
.endm
.macro icebp
.byte 0xf1
.endm
